Electric vehicle sound enhancement

Abstract

Control of an AC motor includes rotation over an operating speed range with the output from an inverter by operating the inverter at switching frequencies that vary in proportion to rotor speed. The operating speed range is parsed into a plurality of speed regions and the switching frequencies within each operating speed region may correspond to a respective pulse ratio that is different from the respective pulse ratio corresponding to an adjacent speed region.

Description

INTRODUCTION[0001]This disclosure is related to electric motor control.[0002]Electric vehicles, including hybrid electric vehicles, include at least one rotary traction motor for producing propulsion power. Brushless AC motors are a popular choice for propulsion motors. AC motors include a stator including one or more phases of AC power. Typically, AC propulsion motors are polyphase and employ three or more phases of AC power to generate a rotating magnetic field in the stator to drive the motor's rotor.[0003]Electric and hybrid vehicles may include a high voltage (HV) energy storage device (ESD) for providing power to drive the propulsion motor(s) and to low voltage (LV) applications. ESDs are typically electrochemical devices. Inverters are employed to convert the DC power of the ESD to AC power to drive the propulsion motor(s) by way of a rotating magnetic field. Inverters may be bidirectional and operated to convert AC power from the propulsion motor operating in a regenerating ...

AI Technical Summary

Benefits of technology

This patent is about an apparatus and method for controlling the speed of an AC motor using a DC power source and an inverter. The inverter converts DC power to AC power to drive the AC motor. A processor is used to analyze the motor's speed range and determine the optimal switching frequencies for each speed region. The switching frequencies are used to maintain the inverter's pulse ratio to a predetermined profile, which can produce either continuous or discontinuous switching orders in adjacent speed regions. The apparatus and method can also use frequency dither and limit the inverter's operation to specific switching frequencies. The technical effect of this patent is to provide an efficient and effective way to control the speed of an AC motor using a DC power source and an inverter.

Problems solved by technology

Inverter switching frequencies are known to induce audible noise within the polyphase bus structure, the propulsion motor, propulsion drive unit and any other mechanically coupled structures including final drives, axles and vehicle structure.

Such inverter induced noise is primarily at the switching frequency of the inverter and certain proximate sidebands and may be highly tonal and sharp in pitch, therefore generally objectionable.

Noise, vibration, harshness experts go to great lengths to attenuate this noise as many end users may find it objectionable and nonintuitive in an automotive environment.

However, while some success at noise isolation and decoupling is possible, a certain level of noise is inevitably coupled into the passenger compartment of the vehicle and will reach the occupants' ears.

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